(a) Field of the Invention
The present invention relates to a method for correcting a photo-contiguous effect during manufacture of a semiconductor device, more in detail, to the method for correcting the photo-contiguous effect, which prevents undesired reduction of a length of a pattern at a node where two layers are electrically connected.
(b) Description of the Related Art
In a photolithographic step used in the process for manufacturing a semiconductor device having miniaturized patterns, a photo-contiguous effect may occur which does not perform an accurate transfer of pattern due to photo-interference generated between rays contiguous with each other during an exposure step and a transfer step. Reduction of an error regarding pattern sizes generated by the photo-contiguous effect is required. The pattern size error can be reduced by correcting the photo-contiguous effect as described in JP-A-5(1993)-80486. The correction is conducted by modifying a projection of a pattern to be corrected by means of a calculation technique as described in JP-B-2616467.
When a line end of a circuit pattern such as an interconnect pattern and a gate pattern is connected to a connection node such as a plug and a via hole, a problem arises that the line end of the interconnect or the gate is reduced in length due to the photo-contiguous effect to decrease the connection area down to smaller than the design area, resulting in connection deficiency.
A conventional technique of modifying a mask pattern for canceling the reduction of the line end of the connection node is shown in FIG. 1.
In the conventional technique, a pair of additional patterns 102 and 103 having a projection "a" and a length "b" are provided at respective corners C1 and C2, of the end of an interconnect 101 in an interconnect pattern.
The projection "a" means the amount of projection of the side of the additional pattern with respect to the side of the corresponding side of the interconnect.
Such additional patterns 102 and 103 are also reduced due to the contiguous effect to achieve the interconnect 101 having the overall shape complying with the original design.
In the conventional technique as shown in FIG. 2, additional pattern 106 is also provided to each bent of non-connection node 105 having one free corner, in addition to the connection nodes 104 having plugs and two adjacent free corners. This modification or correction is also conducted to the nodes where the modification is unnecessary. The technique conducting the modification regardless of the existence of the plug significantly increases the size of the mask pattern data due to increase of the number of figures of the additional patterns. Further, the additional pattern having the same length of projection is added regardless of the length of the side of the connection nodes 104, increasing the amount of modification for the shorter side of the pattern to deteriorate the resolution at the shorter side.
FIG. 3 shows a known technique of correcting the photo-contiguous effect in connection of the length of the side. The technique adds an additional pattern 107 having projections "a" and "d" different from each other corresponding to widths W1 and W2 of both sides of the pattern 101 to be modified. Although the amount of the modification at the shorter side is not excessive in the technique, calculation of the projections for the both sides causes a problem that a long period of time is required for obtaining the projections.
Accordingly, a method for correcting the photo-contiguous effect is desired in which an amount of modification is appropriate, increase of a period of time for modifying a pattern is not so large, and the modification can be applied only to required nodes.